Reviews & Analysis

Instrumental records show that El Niño is highly variable in space and time. Now a thousand-year-long record from trees in the southwestern United States reveals even greater extremes, and a possible link between El Niño activity and climate warming.

Comparing changes in temperature and solar radiation on centennial timescales can help to constrain the Sun's impact on climate. New findings regarding the minimum activity level of the Sun reveal that comparisons made so far may have been too simplistic.

Mounting evidence that climate change will impact food security demonstrates the need to adapt food systems to future conditions. New work sheds light on the measures that will be needed to do so, and what the gains of implementing them might be.

Laboratory studies indicate that warming can eventually push cold-blooded organisms past their physiological limits, with detrimental effects on growth. Now evidence from the field indicates that this phenomenon is occurring in the Tasman Sea.

The climate impact of biofuels is usually considered in terms of their net effect on greenhouse-gas emissions. The expansion of sugar cane into pastureland for biofuel production is now shown to also exert a direct local cooling effect.

Warming of the upper ocean may stimulate plankton metabolism, enhancing photosynthesis. This effect has received little attention, but new research suggests that it could be important enough to spur a net increase in global ocean productivity.

The Clean Development Mechanism was designed to allow emissions reductions and sustainable development to proceed hand-in-hand. Analysis now addresses the question of whether — 14 years after its creation — it can be reformed sufficiently to serve current needs.

Flowering plants have expanded rapidly in Antarctica over the past 50 years. A study now reveals that an efficient way of acquiring nitrogen from protein-rich soils as they decompose has allowed these plants to take full advantage of a warming climate.

Contrails formed by aircraft can evolve into cirrus clouds indistinguishable from those formed naturally. These 'spreading contrails' may be causing more climate warming today than all the carbon dioxide emitted by aircraft since the start of aviation.

Recovery of the ozone hole and increasing greenhouse-gas concentrations have opposite effects on the jet stream. New model experiments indicate that they will cancel each other out over coming decades, leaving storm tracks at a stand still.

Explaining climate risks and uncertainties to non-specialists is fraught with difficulties. An array of principles and guidelines has been developed to aid this process, but there is little evidence for their efficacy. An empirical approach is thus needed to identify the communications approaches that will effectively convey the practical implications of large, complex, uncertain physical, biological and social processes. An ambitious interdisciplinary initiative will be required to deliver effective climate science communication, including institutional support to sustain it.

Engaging the public with climate change has proved difficult, in part because they see the problem as remote. New evidence suggests that direct experience of one anticipated impact — flooding — increases people's concern and willingness to save energy.

The impact of climate change on food production remains uncertain, particularly in the tropics. Research that exploits the results of historical crop trials indicates that Africa's maize crop could be at risk of significant yield losses.